Conventionally, a storage battery that is charged and discharged repeatedly is disconnected from a main circuit when an anomaly occurs such as over-discharging or overcharging, generation of excessive heat over an allowable value, or a fault in a control system that controls the storage battery. To immediately disconnect the storage battery from the main circuit, a circuit breaker is provided therebetween.
Storage batteries are used, for example, as a power source for driving a vehicle. Such storage batteries are installed in, for example, electric locomotives which run by a drive power source (motor) driven by electricity from the storage batteries, or installed in hybrid locomotives that include a motor and an engine as drive power sources. Storage batteries may be installed in automobiles such as electric cars and hybrid cars, trucks, and buses. Such in-vehicle storage batteries are used in a more vibrating environment for a longer period of time than stationary storage batteries. Similarly, controllers of the storage batteries and circuit breakers are likely to be used in a harsh environment. Thus, vehicle-use storage batteries tend to be required to implement a higher level of expected safety design and reliability than stationary storage batteries.